python2 string

1. string object and unicode object
   s = 'abc' # s is a string object
   s = u'abc' # s is a unicode object

2. encode method
   It's a little more complex in Python 2 (compared to Python 3), since it conflates the concepts of 'string' and 'bytestring' quite a bit. Essentially, what you need to understand is that 'string' and 'character' are abstract concepts that can't be directly represented by a computer. A bytestring is a raw stream of bytes straight from disk (or that can be written straight from disk). encode goes from abstract to concrete (you give it preferably a unicode string, and it gives you back a byte string); decode goes the opposite way.
   The encoding is the rule that says 'a' should be represented by the byte 0x61 and 'α' by the two-byte sequence 0xc0\xb1.